This year on World Population Day let us celebrate the unrivalled success that humankind has had in making the world its home, and in enabling civilisation to thrive... It's in all of our interests for us to achieve what we agreed in London a year ago. Let us make the pledges of the London Family Planning Summit a reality.

"Never prophesy, especially about the future." That nicely captures the perils of predictions - so nicely, indeed, that the saying or a version of it has been credited to numerous people, from the movie mogul Sam Goldwyn to baseball's Yogi Berra.